1. Field of the Invention
The invention relates to a direct injection spark ignition internal combustion engine and a method for controlling the same.
2. Description of the Related Art
When homogenous combustion is performed by injecting fuel on each intake stroke in a direct injection spark ignition internal combustion engine in which fuel is directly injected into each cylinder, the required amount of fuel can be reliably injected into each cylinder as compared to in an internal combustion engine in which fuel is injected into each intake port. However, when fuel is injected toward the top face of each piston, the injected fuel may attach the top face of the piston, and if the fuel on the top face of the piston is not vaporized by the time of ignition and thus fails to be combusted, it produces smoke.
A technology has been proposed in which, in order to suppress the production of smoke, the thrust force of injected fuel is weakened at a low engine temperature where the likelihood that the injected fuel will attach the top face of each piston is low (For example, refer to Japanese Patent Application Publication No. 09-68072).
According to this technology, the amount of fuel that would attach each piston can be reduced by reducing the thrust force of the injected fuel when the engine temperature is low. However, at a high engine temperature where the thrust force of the injected fuel is strengthened, especially when a large amount fuel is injected, a large amount of fuel attaches the top face of each piston. If most of the fuel on the piston is not vaporized by the time of ignition, a large amount of smoke will be produced.